This invention concerns a procedure for bending extruded lengths, in particular wires, tubes, cables, drawn or extruded lengths sections and the like. It further concerns a bending machine to carry out this procedure with two mutually spaced bending devices each comprising at least two bending components and drives to move at least one of the bending components essentially transversely to the length being bent.
Such bending machines are described in the German Offenlegungsschrift No. 16 52 822 and in the German Pat. No. 537,904. They comprise two or more bending devices next to each other each with two bending components. In the bending machines of the first cited document, the spacing between the bending devices is also adjustable so that bending can be carried out at mutually different spacings.
The German Gebrauchsmuster No. 18 81 368 discloses a further bending machine comprising a bending device with roller-shaped bending components. Also, roller guides are provided for the wire to be bent.
In all previously known bending machines, the length of material is bent by applying a curving force to the bending components. The inside bending radius then corresponds to the radius of the bending components. Large bending radii about the size of the particular bending device and above cannot be achieved in such bending methods. Furthermore, the components must be exchanged, when bending radii of different sizes are required, for those with the proper radius.
The object of the invention therefore is to discover a procedure allowing also making large bending radii while using compact bending machines, and where no conversion of the bending machine is necessary when producing bends with different radii.
This problem is solved by the invention in that the length of extruded material will be curved in opposite direction at two mutually spaced sites and simultaneously about two mutually parallel axes which are transverse to the longitudinal axis of the extruded length, essentially without other substantial forces.
In this manner the length to be bent is subjected to a curving or bending moment acting transversely to the longitudinal axis of this length, and this is done by a pair of forces applied at two spaced sites. Due to the application of such a bending torque, the length then bends freely and uniformly in the space between the two bending devices. A bending radius is obtained which, unlike the case for the known bending machines, will not depend on the diameter of the bending components, but rather on the spacing of the bending devices at the beginning of the bending procedure. The larger this separation, the greater the bending radius.
To carry out the procedure of the invention, there are basically two alternatives. One alternative is characterized in that the drives operate in opposite directions and in that the bending components each are provided with a freely rotating sleeve. Another solution consists in the drives again operating oppositely and in that at least one of the bending devices is displaceably guided during the bending procedure in a plane perpendicular to the axes of rotations and relative to the other device to impart a torque without additional forces.
In both solutions, the torque is applied in the absence of additional forces by simultaneous drives operating oppositely for each of at least one of the bending components. In the first cited solution, the length to be bent is kept free from any additional forces by the roller-shaped design of the bending components because the length may slip through the bending components while being bent. As regards the last cited solution, no relative motion between the length and the bending components takes place because the bending devices are guided in such a manner that their spacing decreases in relation to the progress in bending. The latter embodiment is especially applicable when bending lengths with rough surfaces such as construction steel, because such materials would hardly slip between the bending components of the first solution. In the second solution, the occurrence of additional forces is avoided by the relative motion of the two bending devices during the bending procedure.
Obviously both solutions may be combined, that is, the displaceable guidance of the bending devices may be combined with roller-like bending components.
If always the same bending radii are to be made using the bending machine of the first solution, then it suffices to keep the bending devices at a fixed distance apart. If however this spacing is varied, then it will be possible to make correspondingly different bending radii. This can be achieved on one hand in that the bending devices are fixed in place at diverse spacings. Alternatively at least one of the two bending devices, but especially both, shall be guided freely. This alternative also is applicable to the second solution. In that case the spacing between the two bending devices can be set automatically in such a manner that only bending torques but no further forces are transmitted to the lengths to be bent. As a result a neat arc of circle shall be achieved, provided that the material involved is uniform in its moment of inertia with respect to length, and this shall be the case as a rule. Therefore; the bending machine of the invention also may be appropriately used to test inhomogeneities in the lengths. If due to inhomogeneity there is a lesser moment of inertia at one place in the length, then a clearly visible and smaller arc shall be formed there.
Appropriately the bending device(s) shall be displaceably mounted in a slot guide which illustratively may be provided in a bench.
The bending components can be moved transversely to the lengths in a simple manner known per se using a rotary drive. The bending components then can be mounted on a rotary disk. Alternatively and obviously there is also the possibility to directly connect the bending components to linear actuators to carry out the transverse motion. The term linear actuator especially includes hydraulic or pneumatic cylinders, also spindle drives or the like.
The flexibility of the bending machine of the invention may be further enhanced by each bending device comprising its own, separately reversible drive. As a result, the rotational shafts can be driven not only oppositely, but also in the same direction, or only one of them might be. In this manner manifold bendings can be carried out.
In lieu of a slot guide, special constrained guide means may be provided, which cause the change in separation required to apply the bending torque in the sense of the second solution. This can be implemented in simple manner in that each of the bending devices is mounted to a pivot system which is pivoted relative to the other(s) by at least one drive means. The pivot systems each may consist of two guide links forming a four-joint kinematics. Appropriately, the guide links always shall be parallel to one another whereby the particular four-joint kinematics shall form a parallelogram. A simple design is given when the guide links are hinged to the bending devices at the shafts of the bending component.
In order that the guide links and hence the bending devices always be mounted with mirror-symmetry to each other, one guide link of one bending device shall be synchronized by a gear unit with a guide link of the other bending device. This can be implemented in simple manner by two mutually meshing gears or gear sectors. The gear transmission will be especially simple if one of the guide links rests in the pivot axis of the associated four-joint kinematics so that its hinge point performs only a motion of rotation.
To make possible simple displacement of the two four-joint kinematics, they should be suspended from a pivotably supported drive bar, preferably in a V-arrangement with close-by pivot axis.
The free ends of the drive bars can be connected to the drive motor. It was found appropriate in this respect to connect the drive bars to two pressure bars which are joined together and form a link quadrilateral acted on by the drive motor. In this embodiment, both bending devices are operated from a single drive motor, which represents an advantageous design for a hand tool because saving weight. In that case the drive motor illustratively is a pressure cylinder with return spring. However other drives, for instance electrical ones, or exceptionally, hydraulic ones, also may be used.
Regardless of the manner in which the two bending devices are being moved, it may be appropriate that one bending component of each bending device be located in the pivot axis and therefore act only as a bearing. In that case only one of the bending components will be moved transversely to the lengths being bent.
The versatility of the bending machine is further enhanced when the bending components are mounted in exchangeable manner, whereby bending components of various diameters can be mounted. Again, the spacing between the bending components of each bending device shall be adjustable to further improve adaptability.
A further feature of the invention provides that the bending components conically taper toward their free ends. This makes it possible to insert the lengths to be bent without play between the bending components. In this manner uniform bending at equal angles of rotation may be achieved regardless of the material thickness.
Lastly the invention provides mounting a compression piece between the bending devices so as to prevent forming an arc of circle, whereby a U bend with straight connections between the corner bends can be made.